1) Do you want to center it for mobile only? Then add the following code in Theme Options > Stylng > Custom CSS
@media only screen and (max-width: 480px){
.footer .widget_media_image, .footer .widget-title {text-align: center;}
}
2) This is default content of the sidebar. If you want to disable sidebar for the page then do using 8theme Layout Options for your page http://xstore.helpscoutdocs.com/article/45-8theme-page-post-layout-settings-8theme-post-options (Make sure CMB2 plugin is enabled to get these options) Or if you want to place your own content to the sidebar go to Appearance > Widgets > add widget into Main Sibear widget area, add empty text widget if you just want to clear default content of widget area.
3) Add the following custom to fix the problem .nav-sublist-dropdown {top: 40px !important;}
